ΔE 20.3, loose: different enough that you should pick on purpose. Flat Flesh is much more saturated, warmer than Dark Yellow Sandy Yellow.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Flat Flesh is much more saturated, warmer than Dark Yellow Sandy Yellow.
The same difference applies the other way round: Dark Yellow Sandy Yellow is much more muted, cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Dark Yellow Sandy Yellow on the colour wheel See Flat Flesh on the colour wheel
All matches: Dark Yellow Sandy Yellow equivalents · Flat Flesh equivalents